Method of bending and drawing sheet metal.



N. A. ROBERTSON. METHOD OF BENDING AND DRAWING SHEET METAL.

APPLICATION FILED MAY 8, 1912. 1,078,958. Patented Nov. 18, 1913.

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N- A. ROBERTSON. METHOD OF BENDING AND DRAWING SHEET METAL.

' I APPLICATION FILED MAY 8, 1012. 1,078,958.

Patented Nov. 18, 1918.

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APPLICATION FILED MAY8,1912. 1,078,958. Patented Nov. 18, 1913.

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NORMAN A. ROBERTSON, OF NEW YORK, N.

METHOD OF BENDING AND DRAWING SHEET METAL.

Specification of Letters Patent.

Patented Nov. 18, 19513.

Application filed May 8, 1912. SerialNo. 695,981.

To all whom it may concern:

Be it known that I, NORMAN A. Ronnn'r- SON, a citizen of the United States, residing in the borough of Brooklyn, county of Kings, city and State of New York, have invented certain new and useful Improvements in Methods of Bendin and Drawing Sheet Metal, of which the ollowing is a specificition.

This invention aims to provide an improved method of bendin and drawing sheet metal,.such for examp e as iron or steel or aluminum, and especial for drawin the irregularly-shaped parts 0 the bodies 0 antomobiles and similar vehicles.

Automobile bodies usually comprise a supportin floor, and sides and-ends which inclose t e seats. The sides and ends have been-made of plates of metal some or all of which are bent both in a longitudinal and in a transverse direction so as to roduce convenient and graceful shapes. xcept at the corners between the sides and the ends the curvature of the plates has been comparatively slight, and it has been the practice heretofore to shape the plates by hand, at a ver considerable expense.

'I his invention provides for the drawing of the plates into the desired shape entirely y machinery, thus securing greater accuracy and economy than can be secured by hand work.

In the accompanying drawings, Figures 1, 2 and 3 are respectively an elevation, inverted plan, and section (on the line 33 of 'Fi '1) of a plate adapted to form the rear on of an automobile body; Figs. 4, 5, 6 and 1? illustrate a suitable machine for making the end plate of Figs. 1, 2 and 3; Fig. 4 being a front elevation, partly in section, Fig. 5 being a horizontal section on the line 5-5 of 4, Fig. 6 a central transverse section, an 'Fig. 7 an end elevation.

The article shown in Figs. 1, 2 and 3 is an unfinished end late or seat back and is se- 'lected as ty ica of the numerous different shapes which can be made according to the principles of this invention. Calling the distance from right to left in the drawing the plates are stifi'ening blank the punch, clamp length of the sheet, Fig. 2 shows that it ,is curved longitudinally to form the center A and the end portions B at approximately a right angle to the centnal portion; and

shows that the central portion is curved transversely, the curve being of slight degree and being of reversed or S-shape. Ad-' acent to the upper and lower edges of the ribs 0 and D stamped therein. Similar intermediate ribs F are formed in the back or central portion. The ends of the plate are unfinished, being subseguently trimmed and bent in any usual or suitable press.

In shaping the plate, the blank is held .at two op osite sides, and left freeat the other two s1 es. For example, for making the plate of Fig. 1 it would be held only at the end ortions B. Notwithstanding that the blan is free at the top and bottom sides, it is drawn into a shape which is-curved in the transverse direction as well as in the lon itudinal direction, the holding of the ends eing suflicient to permit the limited amount of transverse shaping required. It is possible in fact to secure most of the sha es desired by the mere pressure of the-siia ing punch upon one face of the sheet, wit out the necessity of an opposing die, the desired shape being obtainedby the mere stretching of the metal over the punch by reason of the relative movement between the punch and the clamped ends of the blank.

Various types of machine may be used for securing the clamping of the ends of the and the desired relative movements of s, and die. In the machine illustrated a pair of blank holders or grippers G are located at each side of the ma:

chine, being removably mounted on blocks H which are mounted, one at each side of the machine, on the upper ends of a pair of lungers H which work in hydraulic cyliners J thblocks H at o posite sides being connected to each other y means of cross bars K, and the cylinders J being mounted on a cross-head or platen L on the top of the plum er M of the main ram .by which the punc N is raised and lowered. The upper it while holding its ends die 0 is fixed in the upper press head O and carries removable grippers P. The upper grippers P and the lower grippers G are made detachable, so that grippers of differ ent shapes may be put into the machine for making plates having diilerently shaped ends.

The cylinders J are connected to any usual or suitable type of accumulators whereby a constant hydraulic pressure is maintained on the plungers II, this pressure being calculated to permit a drawing of the sheet through the grippers with considerable friction as the punch advances, and being adjustable to different pressures. The punch N is mounted on a frame It which is provided with projectin lugs S which engage the upper edges of the tie bars K so as to hold the grippersG away from the blank until thepunch commences'to advance; afterwhich. the blank is gripped with a constant pressure during the entire drawing opera-- tion, the lugs S rising clear above the tie bars ii. The punch N and die 0 are removable like the grippers l and G to adapt the machine for bending plates of ditl'erent shapes. While other types of machine may be used, the machine illustrated is especially designed for the work in question and has substantial advantages in doing such work. The attachment of the cylindersJ to the ram makes a perfectly simple and very strong construction which works automatically to first clamp with a substantially constant pressure suiliciently slight to prevent tearing the blank. The grippers G are inclined on their ends and there is consequently a strong lateral force acting against the grippers and the blocks H. But these blocks bear inward against the punch N and are thereby absolutely held against yielding.

The ends of the blank may be quite long and weighty and the faces of the grippers G and P are inclined to give a substantial downward incline to the extending ends of the blank, thus minimizing the difliculty of drawing them through the grippers.

The blank Q, being placed in the machine,

its ends are gripped with a determined pres sure at the first upward movement of the punch. During the further movementof the punch the ends, though permitted to slip as far as necessary, are held with considerable firmness, so that they first draw the comparatively thin metal closely over the punch and make it fit the unch, somewhat in the manner in which a no v glove is drawn over ones hand, and thereafter permit the ends to slide through the grippers as the punch advances. I prefer to provide ribs T on the punch and corresponding grooves U on the die, for forming the stiffening ribs the blank and then draw in the plate; because the ribs T on the punch appear in practice to give the punch a. better grip on the sheet even before the latter is pressed clear up to the 'die. To secure the general curves'desired it is not necessary to press the sheet clear against the die, the drawing of itover the punch, alone being suflicient with some shapes and metals. In other cases it may bemade to bear against the die where the shape desired is diilicult to secure otherwise. Or, as in the case illustrated, the punch may be made to carry the blank against the die throughout the entire area of the blank, and such contact is necessary to form the sharply curved stifi'ening ribs After the drawing operation in the machine illustrated, the ends of the blank may be trimmed and further bent, drawn, or stamped as desired. For example, end ex: tensions B and end ribs C D and E may be formed as shown, in dotted lines, in Figs. 2 and 3.

I do not claim'the apparatus above described in the present application, the same being claimed in a divisional application, pending concurrently herewith.

What I claim is a 1. The method of bending and drawing sheet metal to make parts of vehicle bodies or the like which are curved in two directions and are formed with stiiiening ribs, which method consists in pressing a blank between a punch and a die shaped to pen.

form the desired drawing and bending operations and to stamp the stifiening ribs all at one operation, ho ding the blank at two opposite sides, and leaving it free at the other two sides.

'2. The method of bendin sheet metal to make parts 0% vehicle bodies or the like, which consists in holding two opposite ends of a blank and drawing it over a suitably shaped punch, to cause it to fit the shape of said punch, and thereafter pressing it between sa d punch and a die of suitable shape, releasing its ends suficiently to permit them to move with the punch.

3. The method of bending and drawing sheet metal to make, in a single operation, parts of vehicle bodies or the like which are curved in two directions, which consists in yieldingly gripping two opposite sides of the blank while leaving it free at the other two sides, and drawing it to the desired shape by stretching it over a punch having a face of the required contour, and thereby drawing the metal unequally between its gripped edges to bring it into conformity with such contour.

a. The method of bending and drawing sheet metal to make, in a single operation,

and drawing" curved in two directions, which consists in yieldingly grilpping two 0 posite sides of the blank whi e leaving it ree at the other two sides, and drawing it to the desired shape by stretchin it over a, punch having a face of the requlred contour, and thereby drawin the metal unequally between its grippeci edges to bring 1t into conformity with such contour, and finally squeezing the Witnesses sheet between said punch and a die con- 10 formed thereto.

In witness whereof, I have hereunto si ed 111 name in the presence of two subscri ing witnesses.

NORMAN A. ROBERTSON.

THOMAS F. WALLACE, FRED Wm'm. 

